1. Field of the Invention
This invention relates in general to vehicular axle assemblies and in particular to a method for joining together vehicle components, especially those manufactured from dissimilar materials, to form such a vehicle axle assembly.
2. Background of the Invention
Axle assemblies are well known structures that are in common use in most vehicles.
Such axle assemblies include a number of components, which are adapted to transmit rotational power from an engine of the vehicle to the wheels thereof. Typically, an axle assembly includes a differential assembly that is rotatably supported within a non-rotating carrier. The differential is connected between an input drive shaft extending from the vehicle engine/transmission and a pair of output axle shafts extending to the vehicle wheels. The axle shafts are contained in respective non-rotating beam portions, which are secured to the carrier. Thus, rotation of the differential by the drive shaft causes corresponding rotation of the axle shafts. The carrier and the beam portions form an axle housing for these drive train components of the axle assembly, inasmuch as the differential and the axle shafts are supported for rotation therein.
Axle housings are generally classified into two basic types. The first axle housing type is a unitized carrier construction, commonly referred to as a Salisbury or Spicer type axle assembly. In this structure, the carrier (which houses the differential assembly) is directly connected to the two beam portions (which house the rotatable axle shafts). An opening is provided at the rear of the carrier to permit assembly of the differential therein. A cover closes this opening during use. Unitized carrier axle housing constructions of this type are economical to manufacture and are readily adaptable for a variety of vehicles.
The second axle housing type is a separable carrier construction. In this structure, the axle beam portions are connected together by a central portion of the axle housing that is formed separate and apart from the differential carrier. This central portion is generally hollow and cylindrical in shape, having a large generally circular opening formed therethrough. During assembly, the differential is first assembled within the carrier, then the carrier is secured to the central member. The overall shape of this type of axle housing (i.e., the generally round shape of the central portion and the elongated beam portions extending therefrom) generally resembles the shape of a banjo musical instrument. Hence, this type of axle housing is commonly referred to as a banjo type axle housing. Banjo type axle housings are advantageous because the carrier and differential can be removed from the axle assembly for service without disturbing the other components thereof. In addition, the beaming loads of the vehicle weight are carried via a separate structure from that structure which orients and rotatably supports the differential assembly and the ring and pinion set. Because of this separation of function, banjo-style axles will support higher vehicle weights than a Salisbury-style axle assembly of similar size.
In the past, several methods have been employed to form axle housings, and many of these methods employ welding to form the housing.
In the past, virtually all of these axle assemblies have been manufactured from a metallic material. Steel has traditionally been the preferred material for manufacturing all of such vehicle axle components because of its relatively high strength, relatively low cost, and ease of manufacture. As mentioned above, vehicle axle housing assemblies manufactured from metallic materials have been secured together by conventional welding techniques. More recently, however, in an effort to reduce the weight of the vehicle axle assembly, it has been found desirable to use alternative materials to form some or all of the vehicle axle components. Thus, in some instances, it may be desirable to form some or all of the vehicle axle components from materials which cannot be easily secured together, or in some cases cannot be secured together at all by conventional welding techniques. For example, conventional welding techniques cannot be used to secure a metallic vehicle axle component to another non-metallic vehicle axle component. Thus, it would be desirable to provide a method for joining vehicle components together to form a vehicle axle assembly, where the components are formed from alternative materials, and particularly those components manufactured from dissimilar materials, such as cast iron or aluminum carrier housings and fiber-reinforced composite tubes.